Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of a third image thereof; and,

FIG. 4 is a front view of a fourth image thereof.

The broken lines in the drawings illustrate portions of the display screen with a transitional graphical user interface that form no part of the claimed design.

The appearance of the images sequentially transitions between the images shown in FIGS. 1 through 4. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 